The present invention relates to a rotor structure of an alternating current generator for use in a vehicle; and, more particularly, to a rotor structure of an alternating current generator for use in an automobile in which the rotor structure has an improved insulating bobbin for insulating a field magnetic coil, suitable for use in an automobile.
In an alternating current generator for use in a vehicle, a need for obtaining a high output is increasing year by year; and also, in accordance with a directing desire for a higher quality alternating current generator by the end user, a requirement for reducing noise, such as magnetic noise generated in the alternating current generator, has become more important.
In a conventional rotor structure of an alternating current generator for use in a vehicle, a bobbin for insulating a rotor core from a field magnetic coil in the rotor structure of the alternating current generator for use in the vehicle is disclosed in, for example Japanese patent laid-open publication No. 20,763/1985.
Namely, in the above stated conventional rotor structure of the alternating current generator for use in a vehicle, a pressing portion is formed integrally with the bobbin. This pressing portion is inserted between an inner peripheral face of a claw-shaped magnetic pole of the rotor core and the field magnetic coil; and, accordingly, the resonance vibration generated on the claw-shaped magnetic pole of the rotor core is reduced.
Besides, another conventional rotor structure of an alternating current generator for use in a vehicle having a flexibility vibration attenuation member is disclosed in, for example, Japanese patent laid-open publication No. 182,461/1983.
This flexibility vibration attenuation member is made of an insulating material and is made to closely adhere to a portion between an outer peripheral face of a claw-shaped magnetic pole of a rotor core and an inner peripheral face of a field magnetic coil of the rotor structure of the alternating current generator.
In general, during the generation of the electric energy in the alternating current generator, it is well known that, in case an uneven air gap is formed between the rotor core and the stator core, the magnetic noise increases.
According to the above-stated former conventional technique, since the pressing portion is formed integrally with the bobbin, this pressing portion is inserted in full contact with the portion formed between the inner peripheral face of the claw-shaped magnetic pole of the rotor core and the field magnetic coil in the rotor structure of the alternating current generator.
Consequently, in a case where an adhesive material is used to further heighten the strength of the claw-shaped magnetic pole of the rotor core and the magnetic coil, there is a possibility that a varnish material, which works as an adhesive material, insufficiently impregnates into a root portion on the inner peripheral face of the claw-shaped magnetic pole of the rotor core. Accordingly, there is some doubt about the strength of adhesion of the claw-shaped magnetic pole of the rotor core with the magnetic coil.
Further, in the above stated latter conventional technique, the flexibility vibration attenuation member is caused to closely adhere to the portion formed between the inner peripheral face of the claw-shaped magnetic pole of the rotor core and the field magnetic coil in the rotor structure of the alternating current generator.
Thereby, even in a case where a hole portion or a cut-off portion is partially provided in the structure shown in the latter conventional technique, similar to the former conventional technique, there is a possibility that the varnish material, which works as an adhesive material, insufficiently impregnates into the root portion on the inner peripheral face of the claw-shaped magnetic pole of the rotor core in the rotor structure of the alternating current generator.